Lemma practice generator river-crossing #18,800 · Puzzles · Crossing puzzles
Ferrying a group across
A ferry can carry 20 people, one of whom must bring it back. How many trips across (not counting returns) are needed to move 339 people?
Stuck? A gentle nudge
No hints for this one.
Your answer
Loading the math keyboard…
Type naturally — sqrt, pi, / and ^ become notation. Any equivalent form is accepted. Press Enter to check.